Although absolute serum KL-6 levels at neither baseline nor the onset of ILD could discriminate between life-threatening and non-life-threatening EGFR-TKIs induced ILDs, the ratio of serum KL-6 level at the occurrence of EGFR-TKIs induced ILD to that at baseline was found to quite precisely do so. The gene discussed is MUC1; the disease is interstitial lung disease.